For external plaster do I need render mesh. The walls aren't cracked and have been up a good while. I am going to damp proof it with unibond before rendering with snowcrete / lime / sharp sand.

Would a glass fiber mesh be up to the job?

I've read I need an air entraining agent to keep flexibility in frosty conditions. Is there any cheap stuff you would use, or household product???

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More details please - external plaster - what is it that you are plastering ?

Render mesh is normally aluminium EML (expanding metal lathe) and only really needed if the wall is shot to pieces or painted (plaster will not bond properly to a painted wall)

Unibond ? PVA ? - Not on external work my friend, use an SBR slurry mix or rend aid it

Let me know what it is you are plastering and I'll try and help out

You also want EML over any wood / battens etc.

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Cheers guys. I am rendering a breeze block wall about 3m by 6m, the top few courses of which are thermalite blocks, lower ones concrete. I want to a white finish I hope to have bought the right stuff in snowcrete (but also have supplies of lime, portland, sharp sand, fine sand). I was going to go for a couple of layers. I am keen for it to be a bit water resistant to keep the wall as warm as possible.

1st layer:
Portland: Lime : Sharpsand
1.1.6

Don't know about the snowcrete layer

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Have never used snowcrete as I use Weber Pral M through colour renders if I need a colour but I'm sure someone will advise in due course

Get your scratch coat on especially if you have different substrates - thermalite will pull in like a sponge so get your suction even all over - ratio 4:1 - dash of waterproofer in the scratch coat

I like to leave a couple of days before top coat but make sure your top coat is a weaker mix than the scratch -I always go 5:1 ratio

Your scratch coat ratio seems a bit weak at 1:1:6 - and take time to get your scratch coat nice and flat - it makes the top coat alot easier to float up

Good luck, keep us posted

Okay. On the Blue Circle website it says the snowcrete can just be used like normal portland.

So 1.1.4 with scratch coat + Cementone Cemplas air entrainer + no nonsense waterproofer

and

Top coat 1.1.5 + Cementone Cemplas air entrainer + no nonsense waterproofer

Job done

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if snowcrete is similar to a cement additive to obtain a colour then use a level bucket every time you add one to the mix to make sure it is exact for every mix you make, nothing worse than trying to colour match this way its bang on every time.

Other than that its pretty much as pristine states and use either plastic or stainless beads for any angles.